When estimating the amount of disk space required for your backup repository, you should consider a number of factors, including total size of VMs being backed up, backup method, backup frequency, and retention period. You also need to make assumptions on compression and deduplication ratios, change rates, and other factors.
To analyze your VMs’ change rate and calculate the potential amount of space required on the target repository, use the VM Change Rate Estimation report. This report calculates the anticipated amount of VMs’ changed blocks by extrapolating the VMs’ historical write rate data.
Take the following steps:
1.Open Veeam ONE Reporter.
2.Go to the Workspace tab and select Infrastructure Assessment > VM Change Rate Estimation report.
3.Specify the required Scope for which VM data will be reported, Reporting period you need (for example, past week), and Top – this is the number of VMs with the biggest/least change rate.
3.After that, click Preview and wait for the report generation to complete. Review the amount of data written during the specified observation interval (for example, daily). You can access the detailed write performance statistics for each VM’s virtual disk – for that, click the name of the target machine shown in the chart.
You can then utilize this information to estimate the amount of free space that should be available on the target repositories, as well as for the bandwidth requirement estimation.
A test environment includes 10 VMs, 100GB each, 80GB avg/used, with 5% daily change rate and 2:1 estimated compression/deduplication. With the reverse incremental backup method in use by daily backup and 30 days retention, the following estimations can be made:
Estimated Full Backup Size:
10 * 80GB (Used space) * 50% (2:1 Compression) = 400GB
Estimated Reverse Incremental Size:
10 * 80GB * 50% (2:1 Comp) * 5% (Change Rate) * 29 (reverse incremental restore
points) = 580GB
Estimated total Backup Size:
400GB + 580GB = 980GB
For more detailed recommendations, refer to the Veeam Backup & Replication Best Practices document.